textproduct: Rapid City

KEY MESSAGES

- Warm temperatures generally in the 80s and 90s will continue this week, but change is possible by next weekend.

- Mostly dry until Friday afternoon, if not Saturday.

- Elevated to near-critical fire weather conditions will remain the main concern this week.

UPDATE

Issued at 1038 PM MDT Mon Sep 7 2026

Made no major changes to the forecast this period. Main concern over the next few days will be elevated to near critical fire weather conditions across much of the area as warm and dry conditions continue.

DISCUSSION

(This Evening Through Monday) Issued at 210 PM MDT Mon Sep 7 2026

A trough and associated cold front are in the process of crossing the CWA this afternoon, ushering in drier surface air and generally confining additional chances of showers and thunderstorms to our far eastern counties (Mellette, Todd, and Tripp) through this evening. A few CAMs also try to fire something from far northeastern Wyoming into far northwestern South Dakota, and while confidence is low in this scenario occurring, have brushed light PoPs across this corridor late this afternoon just in case. The parent low pressure center our trough/front are connected to is ejecting off the Rockies across Montana, and will deepen as it tracks northeast into Canada over the next couple days. This will keep it too far north/east to offer us additional direct impacts from thunderstorms, but a secondary trough connected to this low will brush across the region Tuesday night/Wednesday morning. So far, any shower/thunderstorm activity with this secondary piece of energy is slated to remain well north of our CWA, but we'll see if that trends any further south in future model updates. Breezy conditions are expected ahead of this trough across the northwestern South Dakota plains Tuesday afternoon, with gusts up to 40 MPH. Broadly speaking, our focus for much of the work week will be on continued warm and dry conditions, which will continue to support elevated to near- critical fire weather conditions each day.

Wednesday onward, somewhat zonal flow through the column is expected until we load up a fresh pair of low pressure systems Friday into the weekend...one crossing Canada to our north and a stronger system moving into the northern Rockies. The Canadian low may offer us a few showers Friday into Friday night, before the stronger second low brings our next organized chance of showers and thunderstorms Saturday and Sunday. This system will moisten up our relative humidity values taking the edge off fire weather concerns, and COULD spell at least a temporary end to the heat! NBM high temperatures currently reach 75 to 85 degrees Saturday, but then hold in the mid-60s to mid-70s Sunday, and the low 60s to low 70s Monday. Unsettled conditions will continue through this time as the low will not yet have cleared the northern Plains. Keep in mind that our actual eventual temperatures will be tied to the strength and track of this low, so stay tuned as we monitor for any trends. 500mb height cluster analysis currently supports the 12z deterministic GFS/ECMWF pretty strongly (our current forecast), but one cluster (11-13 percent of the ensemble space Sunday and Monday, Canadian-heavy) leans into a weaker/further north track with more of a ridging signature over our region, which would keep temperatures considerably warmer and reduce potential QPF amounts. Another cluster each day (another 25 percent of the ensemble space) leans somewhat warmer (and drier) than the other clusters as well. Something to watch.

AVIATION

(For the 06Z TAFS Through 06Z Tuesday Night) Issued At 1118 PM MDT Mon Sep 7 2026

VFR conditions are expected through the period.

FIRE WEATHER

Issued At 210 PM MDT Mon Sep 7 2026

Fire weather will continue to be a concern from now until about Friday this week as warm and dry conditions dominate, with each day ranging from elevated to near-critical. A RED FLAG WARNING continues through 7 PM MDT this evening across most of northeastern Wyoming as well as the Fall River County area. Winds are currently gusting 25-35 MPH across the warning area and thus verifying well. Humidity values have been slow to drop due in part to stubborn cloud cover and delayed surface heating this morning, although some areas are now finally approaching 20 percent and should fall a bit lower this afternoon. Tuesday, RH values will range from 10-20 percent across most of the forecast area, but the gustier winds will shift up over the northwestern South Dakota plains ahead of a shortwave trough that will brush us from the north. At this time, RH values in that area are just a bit high for a Red Flag Warning (20-25 percent), but with wind gusts of 30-40 MPH expected, conditions will be near-critical with grassland fire danger forecast to be very high.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.